Compressed gas power switch

ABSTRACT

The invention relates to a compressed gas switch with two contact pieces, a contact element by-passing the contact pieces when in the on position, and two isolating distances connected to each other in series. The second contact piece opposing the first isolating distance is arranged axially by an annular piston to be displaceable forming a switching chamber. The switching chamber is separated from the heating chamber by a bulkhead partition having a current-dependent valve, and the second isolating distance is produced after opening of a blowing hole located between the second contact piece and the contact element.

FIELD OF THE INVENTION

The present invention relates to a compressed gas power switch, inparticular for extinguishing an arc of a high short-circuit current,which has a first switching piece and a second switching piece,installed on a common axis with a space between them, and an axiallydisplaceable contact piece, which bridges the space when in the on stateand moves away from the first switching piece during switch-off, and isat least partially surrounded by a heating chamber, a second isolatingdistance being connected in series to a first isolating distance formedbetween the first switching piece and the contact piece duringswitch-off.

BACKGROUND INFORMATION

A compressed gas switch is described in principle, for example, inGerman Patent No. 40 10 007 regarding the contact arrangement and theoperation of the axially displaceable contact piece. A heating chamberarranged coaxially with the contact arrangement is described in GermanPatent No. 41 03 119. Regardless of the particular design of thesecompressed gas switches, they have the disadvantage that the hot gasmakes it difficult to establish the isolating distance duringswitch-off, so that the time at which the isolating distance isre-established cannot be determined with sufficient accuracy. Inaddition, controlled switching at zero current is almost impossible,since the inherent delay of the compressed gas power switch is includedin the switching sequence (each compressed gas power switch has adifferent inherent delay determined by the respective manufacturingtolerances, age, environmental conditions, and different masses).European Patent No. 0 334 181 and European Patent No. 0 400 523 describethat a second isolating distance may be connected in series to the firstisolating distance of a compressed gas power switch, but this involves adisproportionately large, and therefore high-cost, drive, since theextinguishing gas may only enter the inside containing the secondarycontact of the second isolating distance from the outside. This,however, means not only that gas must be made available from theoutside, but also that the compressed gas power switch requires a largespace.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a compressed gas powerswitch which allows reliable switching with low drive power and adequatere-establishment of the isolating distance to be achieved regardless ofits particular inherent delay or the hot gas in the heating chamber, yetwithout an increase in the volume occupied by the compressed gas powerswitch.

This object is achieved according to the present invention by the factthat the second switching piece is axially displaceable and is connectedto a piston that may be driven in a switching chamber in respect to thecontact piece by the hot gas flowing from the heating chamber into theswitching chamber so that the second switching piece moves away from thecontact piece.

This provides drive support, since the second switching piece is movedby the extinguishing gas pressure. In addition, the operation of thesecond switching piece depends on the extinguishing gas and therefore onthe current, so that the opening of the second isolating distance iscontrolled by the characteristics of each individual switching sequence.

According to one advantageous embodiment of the present presentinvention, the heating chamber is separated from the switching chamberby a bulkhead, which has a valve controllable through the current to beswitched and the pressure difference between the heating chamber and theswitching chamber. The valve allows the opening time of the secondisolating distance to be controlled with an even greater accuracy.

The present invention may also be advantageously configured so that thesecond switching piece is axially displaceable on the inner periphery ofa tubular main current path connected to the compression piston of acompression device forming a sliding contact, the second isolatingdistance being formed between the second switching piece and the axiallydisplaceable contact piece after a blow hole has been opened by thecurrent-dependent valve via the hot gas driving the piston designed asan annular piston.

Regardless of how the heating chamber is designed, the annular piston inthe switching chamber may be connected to the compression piston of thecompression device via a compression spring, so that after thecompletion of a switch-off sequence, it is ensured that the compressionspring brings the annular piston and the switching piece connected to itback to their original position.

In order to provide a sufficiently large heating chamber for receivingthe hot gases, in particular when switching high short-circuit currents,in another embodiment of the invention the switching chamber downstreamfrom the heating chamber is delimited by a partition running coaxiallywith the switch axis, which is rigidly connected to both the bulkheadand the compression piston of the compression device, so that anadditional heating chamber, connected to the heating chamber upstreamfrom the bulkhead, is formed on the outer periphery of the partition.

According to another feature of the present invention, the valve has oneor two ferromagnetic bodies, which in the high-current phase hold theblow hole in the bulkhead closed against the force of compressionsprings, but open it when the current has reached a certain lower value.The forces of the current of the current path of the compressed gaspower switch, i.e., the forces between the two ferromagnetic bodies in amagnetic field (a concentric magnetic field formed around the compressedgas power switch current path due to the short-circuit current to beswitched off) may be used.

In order to make use of the forces of the current, a ferromagnetic bodyin the form of a cover plate over the blow hole may be slidably arrangedto form a valve. The cover plate is supported by the compression springsagainst the current path formed by the switching piece and the axiallymovable contact piece and its movement is limited by a stop. To guidethe ferromagnetic cover plate taking into account a slight frictionresistance, it is mounted on tracks or in grooves, preferably made ofpolytetrafluoroethylene (PTFE).

The current-dependent valve may also be conveniently made of two coverplates made of ferromagnetic material, which oppose one another at theend face of the bulkhead facing the switching chamber at the height ofthe blow hole and support one another through compression springs.

Both embodiments of the current-dependent valve are also well suited forarrangement on the annular piston at the height of the blow hole;however, in this case it must be ensured that, at least in the area ofthe current-dependent valve, the annular piston not be made of magneticmaterial.

Using the forces arising between two ferromagnetic bodies in a magneticfield, in a preferred embodiment of the invention, the current-dependentvalve may also be made of a frame made of ferromagnetic material,arranged concentrically with the blow hole within the bulkhead and forwhich a cover plate made of ferromagnetic material is provided on theside facing the heating chamber upstream from the blow hole. This coverplate is preferably guided by four rods attached to the bulkhead andsupported against the bulkhead by compression springs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section of a compressed gas power switch according to thepresent invention in the on position.

FIG. 2 shows a section of a compressed gas power switch according to thepresent invention after the first isolating distance is formed in thearea of its contact arrangement.

FIG. 3 shows a section of a compressed gas power switch according to thepresent invention in the off position.

FIG. 4 shows a section of a compressed gas power switch with a firstisolating distance and having a design different than FIGS. 1 through 3in the area of its contact arrangement.

FIG. 5 shows a section of a compressed gas power switch with a secondisolating distance and having a design different than FIGS. 1 through 3in the area of its contact arrangement.

FIG. 6 shows a cross sectional view of a first embodiment of thecurrent-dependent valve of the compressed gas power switches shown inFIGS. 1 through 5.

FIG. 7 shows a cross sectional view of a second embodiment of acurrent-dependent valve of the compressed gas power switches shown inFIGS. 1 through 5.

FIG. 8 shows a third embodiment of the current-dependent valve of thecompressed gas power switches shown in FIGS. 1 through 5.

DETAILED DESCRIPTION

As FIGS. 1 through 3 show, the compressed gas power switch has basicallytwo pin-shaped switching pieces 1, 2 mounted on a common axis, which mayalso have a tubular design; an axially movable contact piece 3, whichcoaxially surrounds and, in the on state, bridges the switching pieces;a first heating chamber 4 concentric with contact piece 3; main currentpath 5 with stationary rated current contact 6; movable rated currentcontact 7; and compression device 8 with compression piston 9.

While FIG. 1 shows the compressed gas power switch in the on position,in FIG. 2 the contact arrangement assumes a position in which, after theprevious opening of main current path 5, the first isolating distance 11is formed after the subsequent separation of sliding contact 10 ofcontact piece 3 from switching piece 1. FIG. 3 shows the compressed gaspower switch in the off position.

Based on this principle of the design of the compressed gas powerswitch, contact piece 3 is now fixedly connected to the area of maincurrent path 5 carrying movable rated current contact 7, and thus toaxially displaceable compression piston 9 through a bulkhead 13, made ofinsulating material and having a blow hole 12. The space behind bulkhead13 is subdivided by a partition 15, coaxial with switch axis 14, into aheating chamber 16 and a switching chamber 17. While heating chamber 16is connected to first heating chamber 4 through an opening 18 inbulkhead 13 thus forming an additional heating volume, partition 15 isfixedly connected with both bulkhead 13 and compression piston 9, andaccommodates, in an axially displaceable manner, an annular piston 21,fixedly connected to second switching piece 2 and subdividing switchingchamber 17 into two partial chambers 19, 20. Annular piston 21 is underthe effect of a compression spring 22 arranged in partial chamber 20. Asfurther shown by FIGS. 1 through 3, compression piston 9 is connected toswitching piece 2 via a sliding contact 23, and the second isolatingdistance 24 is formed after the blow hole 12 has been opened by acurrent-dependent valve after the first isolating distance 11 has beenopened by switching piece 2 and by sliding contact 26 of the axiallydisplaceable contact piece 3.

If a switch-off operation is to be performed on the basis of thisembodiment of the compressed gas power switch, the main current path isopened first. If the distance between rated current contacts 6, 7 issufficient, first isolating distance 11 opens and arc 27 is formed. Thearc 27 heats the gas in heating chamber 4 delimited by isolatingmaterial nozzle 28 with its flow duct, so that the pressure of the gasincreases and, since blow hole 12 is initially closed by thecurrent-dependent valve, it is built up further. As the switch-offcurrent approaches zero, the force acting on current-dependent valve 25decreases and blow hole 12 is opened toward partial chamber 19 ofswitching chamber 17. Therefore, the gas flows from heating chamber 4,and thus also from additional heating chamber 16 into partial chamber19, acts upon annular piston 21 actuating this piston, and thus secondswitching piece 2, opening second isolating distance 24 betweenswitching piece 2 and contact piece 3. Since the current resulting fromarc 27 of the first isolating distance 11, is near zero crossing at thispoint, the extinguishing capability of second isolating distance 24 isnot very high. Additional extinguishing gas may be supplied fromcompression device 8 via opening 30 in compression piston 9.

Thus the invention provides controlled switching at zero currentindependently of the inherent delay of the compressed gas power switch,using low drive power. This results not only in reliable reestablishmentof the isolating distance, but also the effects aimed at by theinvention are achieved without an increase in the size of the compressedgas power switch.

These effects of the compressed gas power switch are also achievedaccording to the embodiment of FIGS. 4 and 5. While FIG. 4 shows theswitch position assumed during a switch-off sequence, in which firstisolating distance 11 is already effective, FIG. 5 shows the compressedgas power switch in the switch position in which second isolatingdistance 24 is already open. This compressed gas power switch differsfrom that of FIGS. 1 through 3 basically by the fact that thecurrent-dependent valve is directly attached to annular piston 21, whichis fixedly connected to switching piece 2 at the height of blow hole 12in bulkhead 13, and annular piston 21 (and therefore also switchingpiece 2) is accommodated in an axially displaceable manner by the areaof main current path 5 carrying rated current contact 7.

Current-dependent valve 25 according to FIGS. 1 through 5 may be eithera current-dependent valve 31 using the forces of the current or a valve32, 33.

In current-dependent valve 31 using the forces of the current accordingto FIG. 6, a cover plate 34, made of ferromagnetic material, isdisplaceably arranged over blow hole 12 and is supported by compressionsprings 35 against current path 36 formed by switching pieces 1, 2 andcontact piece 3. The movement of the cover plate 34 is limited by a stop37.

Current-dependent valve 32 shown by FIG. 7 makes use of the forcesgenerated between two ferromagnetic bodies in a magnetic field. Thus,two cover plates 38, 39, made of ferromagnetic material, oppose oneanother at the height of blow hole 12 and are also supported by oneanother via compression springs 40. Both current-dependent valve 33 andthe one of FIG. 6 are particularly well suited when thecurrent-dependent valve is to be arranged on annular piston 21.

Current-dependent valve 33 of FIG. 8 also makes use of the forcesgenerated between two ferromagnetic bodies in a magnetic field. In thiscurrent-dependent valve 33, a frame 41 made of ferromagnetic material isprovided concentrically with the blow hole 12 within bulkhead 13.Furthermore, upstream from blow hole 12, a cover plate 42 made offerromagnetic material, guided by rods 43 attached to frame 41 andsupported by compression springs 44 against bulkhead 13, is arranged onthe side facing away from heating chamber 4 of the compressed gas powerswitch. The movement of cover plate 42 made of ferromagnetic material islimited by stop 46 with elastic body 45 between them, as shown by FIGS.1 through 3.

Regardless of the design of current-dependent valves 31, 32, 33, theyoperate so that they keep blow hole 12 closed due to their cover plates34, 38, 39, 42, made of ferromagnetic material, being attracted in themain current phase. However, if the switch-off current drops to acertain value, the force of compression spring 35, 40, 44 exceeds theforces of the current, or the forces generated between two ferromagneticbodies in a magnetic field, so blow hole 12 is opened. In the embodimentof current-dependent valve 33 according to FIG. 8, opening of blow hole12 is also supported by the pressure of the gas from heating chamber 4.

What is claimed is:
 1. A compressed gas power switch for extinguishing ahigh short-circuit current arc, comprising: a first switching part and asecond switching part, the first switching part and second switchingpart arranged at a distance from one another along a common axis, thesecond switching part being axially displaceable and connected to apiston movable within a switching chamber, the piston being driven byhot gas flowing from a heating chamber into the switching chamber; anaxially displaceable contact part partially surrounded by the heatingchamber, the axially displaceable contact part bridging the distancebetween the first switching part and the second switching part in an onstate and moving away from the first switching part during a switch-offsequence, the second switching part moving away from the axiallydisplaceable contact part when hot gas flows from the heating chamberinto the switching chamber, wherein a first isolating distance is formedbetween the first switching part and the axially displaceable contactpart, a second isolating distance being generated in series with thefirst isolating distance during actuation of the compressed gas powerswitch.
 2. The compressed gas power switch according to claim 1, furthercomprising: a bulkhead mounted on the axially displaceable contact part,the bulkhead separating the heating chamber from the switching chamber,the bulkhead having a valve controlled by a switchable current and apressure difference between the heating chamber and the switchingchamber.
 3. The compressed gas power switch according to claim 2,wherein the valve includes at least one ferromagnetic part which keeps ablow hole in the bulkhead closed during a high-current phase against aforce of compression springs.
 4. The compressed gas power switchaccording to claim 2, wherein the valve is formed using forces generatedbetween two ferromagnetic parts in a magnetic field, the valve beingformed via two cover plates composed of ferromagnetic material which aredisplaceably opposed to one another in a radial direction with respectto the common axis on an end face of the bulkhead facing the switchingchamber at a height of a blow hole, the two cover plates supporting oneanother through compression springs arranged one of perpendicular andparallel to the common axis.
 5. The compressed gas power switchaccording to claim 2, wherein the valve is formed using forces generatedbetween two ferromagnetic parts in a magnetic field, the valve beingformed via a frame composed of ferromagnetic material, the frame havinga concentric blow hole within a bulkhead, and a cover plate composed offerromagnetic material, the cover plate being guided by rods attached tothe bulkhead, supported against the bulkhead by compression springsarranged one of perpendicular and parallel to the common axis, the coverplate being arranged on the side facing the heat chamber upstream fromthe concentric blow hole.
 6. The compressed gas power switch accordingto claim 1, wherein the second switching part is axially displaceable onan inner periphery of a tubular main current path coupled to acompression piston of a compression device forming a sliding contact,the second isolating distance being formed between the second switchingpart and the axially movable contact part after a blow hole has beenopened by a current-dependent valve via the hot gas driving the piston,the piston being an annular piston.
 7. The compressed gas power switchaccording to claim 6, wherein the annular piston is coupled to thecompression piston of the compression device in the switching chambervia a compression spring.
 8. The compressed gas power switch accordingto claim 6, wherein the switching chamber is downstream from the heatingchamber and is delimited in a radial direction by a partition runningcoaxially with the common axis, the partition being fixedly connected toa bulkhead and to the compression piston of the compression deviceforming an additional heating chamber connected to the heating chamberupstream from the bulkhead on an outer periphery of the partition. 9.The compressed gas power switch according to claim 6, wherein thecurrent-dependent valve includes a cover plate composed of ferromagneticmaterial, the cover plate slidingly arranged over the blow hole andsupported by compression springs against the tubular main current pathformed by the first switching part, the second switching part, and theaxially movable contact part, the compression springs being arranged oneof perpendicular and parallel to the common axis, movement of the coverplate being limited by a stop.